Laryngeal papillomas are rapidly growing, potentially life threatening, benign tumors which have a great propensity for multiple recurrences even after treatment by a multitude of surgical and medical regimes. It has been demonstrated that hematophorphyrin derivative (HPD) is a powerful photosensitizing agent that can cause the destruction of malignant neoplasms when activated by light of appropriate wavelength. Initially I plan to use an experimental cottontail rabbit papilloma virus (CRPV) to induce skin papillomas and to see the efficacy of treatment with photodynamic therapy (PDT) using a red light (wavelength 630 nm). Variables such as total light dose, intensity and exposure time post-HPD injection will be investigated against papilloma tumor response and dermal effects such as edema, erythema and blistering. The histologic process and molecular response which occurs with PDT treated CRPV induced skin papilloma will be investigated at serial time and intervals extending to 36 months. To establish if mucosal papilloma retain HPD, the rabbit oral papilloma virus model will be used. Qualitative data will be obtained by fluorescent techniques, whereas quantitative data will be gathered using Indium-11 labeled HPD. The effects of HPD on the visible and latent viral infection will be evaluated by molecular biologic techniques.